The present invention relates to removing a fluid from a well bore with a chemical wash composition, and more particularly, to chemical wash compositions that comprise water, a sulfonated lignin, and a taurate. These chemical wash compositions may be used to remove or substantially displace a drilling fluid from a well bore.
Fluids are often used for a variety of purposes in subterranean applications. For instance, a variety of drilling fluids have been used in drilling subterranean well bores. As used herein, the term “drilling fluid” may refer to any of a number of liquid and gaseous fluids, and mixtures of fluids and solids (as solid suspensions, mixtures and emulsions of liquids, gases and solids) used in operations to drill well bores into subterranean formations. In some instances, a drilling fluid may be an aqueous-based fluid that comprises clays and/or polymers. During the drilling of a well bore in a subterranean formation, a drilling fluid may be used to, among other things, cool the drill bit, lubricate the rotating drill string to prevent it from sticking to the walls of the well bore, prevent blowouts by serving as a hydrostatic head to counteract the sudden entrance into the well bore of high pressure formation fluids, and remove drill cuttings from the well bore. A drilling fluid may be circulated downwardly through a drill pipe and drill bit and then upwardly through the well bore to the surface.
As the drilling fluid is circulated, a layer of solids referred to as a “filter cake” is formed on the walls of the well bore. The term “filter cake” as used herein may refer to the residue deposited on a permeable medium when a slurry, such as a drilling fluid, is forced against the medium under a pressure. Filter cake properties such as cake thickness, toughness, slickness and permeability are important because the cake that forms on permeable zones in the well bore can cause stuck pipe and other drilling problems. Reduced oil and gas production can result from reservoir damage when a poor filter cake allows deep filtrate invasion. A certain degree of cake buildup usually is desirable to isolate formations from drilling fluids. In openhole completions in high-angle or horizontal holes, the formation of an external filter cake is preferable to a cake that forms partly inside the formation. The latter has a higher potential for formation damage. The filter cake and gelled or partially gelled drilling fluid mixed therewith reduce or prevent additional fluid loss as the well is drilled.
Once the well bore has been drilled to a desired depth, the drill string and drill bit may be removed from the well bore, and a pipe string (e.g., casing, liners, etc.) may be introduced into the well bore. After the pipe string is introduced into the well bore, the well bore may be conditioned by circulating the drilling fluid downwardly through the interior of the pipe string and upwardly between the annulus of the exterior of the pipe string and the subterranean formation. The purpose of this conditioning, generally, is to remove as much of the filter cake and gelled or partially gelled drilling fluid from the walls of the well bore as possible. Unfortunately, however, oftentimes at the end of this conditioning process, the drilling fluid and filter cake remain on the surfaces of the well bore and on the pipe string. This can create problems with subsequent processing, such as in primary cementing operations, inter alia, because the cement composition is generally not compatible with the drilling fluid and/or filter cake. This incompatibility may result in a lack of bonding between the set cement composition and the surfaces in the well bore. This, in turn, may lead to the loss of zonal isolation, as well as other undesirable consequences.
To mitigate the above-described problem, chemical wash compositions containing surfactants and other chemicals have been introduced into the well bore between the drilling fluid and the cement composition. Chemical washes (also called “preflushes”) and spacer fluids perform the same functions. The terms “chemical wash” and “chemical wash composition” as used herein may refer to a fluid, usually water-based, to thin and disperse mud in preparation for cementing. The chemical wash may be pumped ahead of the cement composition to help ensure effective mud removal and efficient cement placement. As the drilling fluid is displaced, the chemical wash contacts the drilling fluid remaining on the well bore and pipe string surfaces to at least partially remove the drilling fluid therefrom. Additionally, the chemical wash should also at least partially remove the filter cake as well. Other specialized chemical washes may be used in the remedial treatment of scales or paraffin deposits in production tubulars.
To mitigate the above-described problem, chemical wash compositions containing surfactants and other chemicals have been introduced into the well bore between the drilling fluid and the cement composition. Chemical washes (also called preflushes) and spacer fluids perform the same functions. A difference between the two, however, is usually recognized in that a spacer fluid is normally densified by adding a material with a fairly high specific gravity such as barite, while a preflush or wash is not so densified. As the drilling fluid is displaced, the chemical wash may contact the drilling fluid remaining on the well bore and pipe string surfaces to at least partially remove the drilling fluid therefrom. Additionally, the chemical wash should also at least partially remove the filter cake as well.
A problem associated with current chemical wash compositions is that due to the chemistry of the compositions, it must be prepared as a liquid, which becomes expensive to ship to remote locations. The current compositions may not be dried because they have a low ignition point, and may readily catch fire if the composition is dried.